This is followed by an incubation period of 2 to 7
days, during which colonization of the involved part of the
intestinal tract and toxin production, invasion or other
disruption of cell function take place.
KNOWING
MEDICINE
The heat-labile toxin or like cholera-toxin binds to a host cell receptor.
ALSO LIKE CHOLERA-TOXIN, THE ACTIVE SUBUNIT
ADENOSINE DIPHOSPHATE RIBOSYLATES THE
REGULATORY SUBUNIT OF ADENYLATE CYCLASE TO
ACTIVATE ADENYLATE CYCLASE . The consequently increased
chloride secretion and reduced sodium absorption combine to cause net
isotonic electrolyte loss that must be replaced to prevent severe dehydration
and hypotension and its potential consequences.
Escherichia Coli
Other strains produce the heat-stable toxin,
a much smaller molecule of 18 to 19 amino
acids (molecular weight less than 2000),
which activates intestinal particulate
guanylate cyclase. Like cyclic adenosine
monophosphate, the cyclic guanosine
monophosphate thus formed also causes
net secretion.
Hemorrhagic colitis associated with the
Shiga-like toxin producing E. coli
(Entero-hemorrhagic E.Coli)
0157:H7, 026:H11, and others, is
characterized by grossly bloody diarrhea
often with remarkably little fever or
inflammatory exudate in the stool.
Although the diarrheal illnesses have been
self-limited, a significant number of
children and adults have subsequently
developed a potentially fatal hemolyticuremic syndrome or thrombotic
thrombocytopenic purpura. haemolytic
anaemia, thrombocytopenia, and oliguric
renal failure. Rapidly developing
hypertension may lead to hemorrhagic
strokes and death in the acute phase. In
still others, management of renal failure
becomes a major clinical problem,
requiring peritoneal or even hemodialysis
before improvement occurs.
Enterotoxigenic E. coli also colonize
the small intestine by means of adherence
factors termed 'colonization-factor
antigens' (CFAs). These adhesins are used
by the organism to attach to host cells via
specific binding-to-host-cell receptors.
The most common clinical manifestation of
Enterotoxigenic E. coli infections is the
watery diarrhea, particularly in young
children. This may range from mild to
severe.
Infection with Entero-invasive
E.Coli is characterized by inflammatory
colitis, often with abdominal pain, high
fever, tenesmus, and bloody or dysenteric
diarrhea essentially like that seen with
Shigella, to which this organism is closely
related. The incubation period is usually 1
to 3 days with the duration usually selflimited to 7 to 10 days.
Outbreaks of Entero-pathogenic
E.Coli infections in newborn nurseries
have ranged from mild transient diarrhea
to severe and rapidly fatal diarrheal
illnesses, especially in premature or
otherwise compromised infants. EPEC
strains are most important as a cause of
endemic diarrhoea in developing countries,